Cancer Cell Overexpression of Death Receptor Modulator

描述（由申请人提供）：免疫系统的正常发育涉及一系列生死决定，这些决定是通过精心协调的信号通路介导的，包括诱导凋亡的细胞死亡受体Fas。Fas介导的凋亡信号消除自身反应并控制活化淋巴细胞的扩张。毫不奇怪，研究表明Fas受体信号通路的改变促进了自身免疫性淋巴细胞增生性综合征和造血癌的发展。造血癌细胞通常表达足够水平的野生型Fas，但由于未知的原因，这种Fas通常具有活化抗性。我们对白血病和淋巴瘤细胞凋亡抵抗机制的理解存在这样的局限性，阻碍了这些癌症治疗的进展。在我们发现病毒编码的Fas抑制剂的基础上，我们预计癌细胞表达类似的Fas抑制剂。事实上，我们的研究已经确定核仁蛋白是一种潜在的Fas结合抑制剂。我们发现过表达的核仁蛋白在淋巴瘤细胞中与Fas结合，并在培养和小鼠中保护Fas凋亡。核仁蛋白敲低使细胞对Fas凋亡敏感。我们假设细胞表面核蛋白直接与Fas相互作用并抑制Fas介导的细胞凋亡，核蛋白代表了癌症治疗的可行靶点。为了验证这一假设，我们将通过分析核蛋白存在和不存在时Fas信号传导，确定核蛋白介导的Fas细胞凋亡调节的可能机制。我们将在核蛋白上定义Fas相互作用域，并产生与Fas缺乏结合的突变体。我们将在小鼠中表达这些缺失突变体，以确定Fas非结合核蛋白突变体是否能防止Fas激活诱导的细胞死亡。我们将在细胞和小鼠中描述核仁蛋白与Fas的分子相互作用。这项分析将建立在发现核蛋白对Fas细胞凋亡具有抗性的基础上。该项目的长期目标是开发直接促进癌细胞凋亡的靶向治疗方法，极大地增强目前的癌症治疗方法。

DESCRIPTION (provided by applicant): Proper development of the immune system involves a series of life-and-death decisions that are mediated through well-orchestrated coordination of signaling pathways, including that of the apoptosis-inducing cell death receptor Fas. Apoptotic signaling mediated by Fas eliminates autoreactive and controls the expansion of activated lymphocytes. Not surprisingly, studies have shown that alterations of Fas receptor signaling pathways promote the development of autoimmune lymphoproliferative syndrome and hematopoietic cancers. Hematopoietic cancer cells commonly express adequate levels of wild-type Fas, but this Fas is often activation-resistant for unknown reasons. Such limitations to our understanding of the mechanisms that cause resistance to apoptosis in leukemias and lymphomas stand in the way of advances in the treatment of these cancers. On the basis of our finding of a virally encoded inhibitor of Fas, we anticipated that cancer cells express similar inhibitors of Fas. Indeed, our search has identified nucleolin as a potential binding inhibitor of Fas. We found that overexpressed nucleolin bound to Fas in lymphoma cells and protected against Fas apoptosis in culture and in mice. Nucleolin knockdown sensitizes the cells to Fas apoptosis. We hypothesize that cell-surface nucleolin interacts directly with Fas and inhibits Fas-mediated apoptosis and that nucleolin represents a feasible target for cancer therapy. To test this hypothesis, we will identify a possible mechanism of nucleolin-mediated regulation of Fas apoptosis in cancer by analyzing Fas signaling in the presence and absence of nucleolin. We will define the Fas-interacting domain on nucleolin and produce mutants that lack binding to Fas. We will express these deletion mutants in mice to determine whether Fas nonbinding nucleolin mutants protect against cell death induced by Fas activation. We will characterize molecular interactions of nucleolin with Fas in cells and mice. This analysis will build on the finding the nucleolin offers resistance to Fas apoptosis. The long-term goal of this project is to develop targeted therapies to directly promote cancer cell apoptosis and greatly enhance current cancer therapies.